Soluble and insoluble-bound phenolics and antioxidant activity of various industrial plant wastes

Abstract

The potential of selected industrial food wastes from juice and nut production including apple peel, apple pomace, pomegranate peel, pomegranate seed, chestnut shell, and black carrot pomace as resources for natural antioxidants was investigated. Soluble free and insoluble-bound phenolics were extracted from the wastes and analyzed for total phenolic and flavonoid contents, phenolic profile and antioxidant activity. Total phenolic and total flavonoid contents of wastes were positively correlated with their antioxidant activity. The highest total phenolic and antioxidant activity were determined in soluble fraction of pomegranate peel due to a significant amount of punicalagin derivatives. Pomegranate peel and seed had the most phenolics and flavonoids in soluble form while other wastes had more than 45% of total phenolics in insoluble-bound form. Chestnut shell showed more antioxidant activity in insoluble-bound fraction compared to that of its soluble fraction. These findings showed that not only soluble but also an insoluble-bound fraction of the industrial wastes has good potential for valorization as a source of natural antioxidants.

High-Value Compounds in Fruit, Vegetable and Cereal Byproducts: An Overview of Potential Sustainable Reuse and Exploitation

“…30-40% of weight) are generated during juice production. Carrot peel, the main constituent of carrot pomace, is known to be rich in phytonutrients, mainly carotenoids, polyphenols, vitamins, and minerals, which exhibit health promoting effects [24]. Carrot peel contains high amounts of dietary fibers, particularly pectin, a soluble dietary fiber consisting of d-galacturonic acid units, l-rhamnose, l-arabinose, and d-galactose, along with other monosaccharides [7].…”

“…Carrot peel contains high amounts of dietary fibers, particularly pectin, a soluble dietary fiber consisting of d-galacturonic acid units, l-rhamnose, l-arabinose, and d-galactose, along with other monosaccharides [7]. In addition, contributions to human health have been attributed to BC from carrots thanks to their antioxidant, antimicrobial and antimutagenic activities [7,24].…”

In Vitro Bioaccessibility of Bioactive Compounds from Citrus Pomaces and Orange Pomace Biscuits

“…Thus, bioaccessibility studies are of critical importance in order to determine the remaining bioactive properties in citrus by-products. These bioactive compounds may be protected from degradation during digestion and food processing by the dietary fiber composing the by-product, as it is known that these phenolic compounds are mainly bound to cell wall structural components (bound phenolics) in fruits and vegetables, such as pectin [8,9]. In fact, thermal processing could enhance the release of bound phenolics by disrupting the cell wall of fruits and vegetables [9], with a consequent increase in their bioaccessibility [10].…”

Acetic acid buffer as extraction medium for free and bound phenolics from dried blackcurrant (Ribes nigrum L.) skins

“…Gulsunoglu et al. (2019) also reported small amounts of p ‐coumaric acid (0.8 ± 0.1 mg/100 g) as bound hydroxycinnamic acid in black carrot pomace. However, it is noteworthy to mention that acid hydrolysis at high temperature might also denature hydroxycinnamic acids in the residue.…”

“…They are bound to protein or cell wall polysaccharides and can only be released by acid, alkaline, or enzymatic hydrolysis treatments. Examples of bound phenolics are high molecular weight proanthocyanidins and hydrolysable tannins, phenolic acids such as ferulic acid, caffeic acid, and sinapic acid (Acosta‐Estrada, Gutiérrez‐Uribe, & Serna‐Saldívar, 2014; Durazzo, 2018; Gulsunoglu, Karbancioglu‐Guler, Raes, & Kilic‐Akyilmaz, 2019; Saura‐Calixto, 2012).…”